The aim of this project is to obtain structural information on polynucleotides and to provide insights into the factors which control structure principally through X-ray fiber diffraction and model building studies. Current areas include 1) the structure of the polyU-spermine complex, 2) prediction of structural parameters from observed helical parameters, and 3) the structure of a polynucleotide-like helical complex adopted by a monomer (G-5'-P).